The invention relates to marine tether anchoring devices.
Various methods are known for fixing tethers of drilling platforms, and the like, in position and it is an object of the present invention to provide an improved marine tether anchoring device which can be released and re-established if necessary and as required.
.Iadd.The use of marine tethers to connect a marine platform to an anchoring chamber is described in U.S. Pat. No. 4,320,993 (Conoco).
U.S. Pat. No. 4,132,147 (Contaldo) discloses in the context of fastening so-called stores to combat aircraft an anchoring device comprising a hollow segmented collet having a passage therethrough and a plug in the passage that is arranged for sliding axial movement relative to the collet between an inoperative position in which the collet is retracted and a working position in which a tapered face of the plug expands the segments of the collet so that the collet cannot pass through the mouth of the anchoring chamber. A protuberant member in the anchoring chamber moves the plug to its working position as the collet travels fully into the base of the anchoring chamber and means is provided for holding the plug in its working position. But apart from the differences of scale and of working environment involved, the Contaldo anchoring device is too complex for marine use and contains essential components such as springs and locking balls that would be prone to corrode in a marine environment and would be inoperable when corroded. Furthermore, in the Contaldo mechanism the collet is fixed to the aircraft and the anchoring chamber has to be pushed upwardly to operate the holding means that keeps the plug in the working position. Such a movable anchoring chamber is manifestly inconsistent with the seabed anchoring chambers taught by Conoco.
U.S. Pat. No. 3,638,988 (Brown) teaches a latch assembly for insertion into the bore of the well tool in which a segmented collet is expanded by an internal plug, but no protuberant means is provided for automatically moving the plug to the working position. U.K. Patent Specification Nos. 1583566 (Fermo) and 1572521 (Schafers) show the use of segmented collets in the context of making fixings in pre-drilled holes in masonry or rock. .Iaddend.